Study suggests low-GI diet may keep cancer away

Cancer survivors wanting to keep a recurrence at bay may want to consider a low-glycemic diet (one light on insulin-spiking refined carbohydrates), according to new research by the Dana Farber Cancer Institute in Boston.

Cancer survivors wanting to keep a recurrence at bay may want to consider a low-glycemic diet (one light on insulin-spiking refined carbohydrates), according to new research by the Dana Farber Cancer Institute in Boston. The federally funded study, published in November in the Journal of the National Cancer Institute, found that of 1,011 patients with advanced colon cancer, those who had the highest “glycemic load” and carbohydrate intake were nearly twice as likely to see their cancer return. Of the 343 patients who saw a recurrence, 262 died.

Meanwhile, taking an additional drug, called irinotecan, in addition to surgery and chemotherapy had no impact on recurrence or survival rates. The study is among the first to look at the role of foods high on the glycemic index (GI) in cancer recurrence and bolsters a growing body of evidence suggesting diet can play an important role in surviving cancer. Colorectal cancer is the second-leading cause of cancer deaths in the United States, with 143,000 cases and 52,000 deaths annually. We asked study author Jeffrey Meyerhardt, MD, a gastrointestinal oncologist, about the findings.

Natural Foods Merchandiser: Why did you do this study?

Jeffrey Meyerhardt: We previously did an observational study in which we asked colon cancer survivors what they ate and followed them over time. We showed that a Western pattern diet—characterized by higher intake of red and processed meat, fat, refined grains and sugary desserts—impacted their risk of recurrence by three-fold compared with those who ate more fruits and vegetables, poultry and fish. We wanted to know which components of that diet may or may not affect someone’s outcome.

NFM: How did you do it?

JM: Stage III patients who had already undergone surgery and chemotherapy agreed to complete questionnaires about 120 foods, as well as their exercise habits and weight during and six months after treatment. We calculated total fructose, total carbohydrate, total gylcemic index and glycemic load (reflections of blood sugar increases after consuming a particular food).

NFM: What did you find?

JM: People who had higher levels of glycemic load and higher total carbohydrate intake on average per week had an 80 percent higher risk of recurrence.

NFM: How could carbohydrate intake promote recurrence of cancer?

JM: We theorize that factors including a high glycemic load may stimulate the body’s production of insulin. That in turn may increase the proliferation of cells and prevent the natural cell-death process in cancer cells that have metastasized (spread) from their original site.

NFM: What is the take-home message for someone who has beaten colon cancer and does not want it to recur?

JM: Changing your diet is not a substitute for standard treatment. This is looking at people already doing chemotherapy and surgery to see what additional protocols derive benefit. It might offer useful guidance for improving patient survival after treatment.

NFM: Do your findings apply to other forms of cancer?

JM: We don’t know yet. Other researchers have been able to study diet and lifestyle with respect to breast cancer recurrence, but there have not been specific studies looking at carbohydrates and glycemic load. We do know weight loss seems to impact outcome for breast cancer patients.

NFM: What should you eat if you want to avoid getting colon cancer in the first place?

JM: The diet that has had the most association with developing colorectal cancer has been one heavy in red meat and processed meat. To some degree, things that affect people’s insulin levels also seem to have some effect. I would say no more than two servings of red meat per week would be ideal, along with avoidance of most processed meats containing nitrates and a substitution of whole grain for refined grain whenever possible.

While studies have long shown that certain dietary habits may predispose people to developing certain cancers, colleagues say Dr. Jeffrey Meyerhadt’s study in the Journal of the National Cancer Institute breaks new ground by making a strong case that what a cancer patient eats may significantly impact his or her survival.

“It is an important study and it advances the field,” says Somdat Mahabir, PhD, a nutritional epidemiologist with the National Cancer Institute.

In an editorial accompanying the study, oncologist Neal Meropol of Case Western Reserve Medical Center in Cleveland notes that after 20 years of clinical trials, only 70 percent of stage III colon cancer patients can be cured with chemotherapy and surgery. “We must look beyond these traditional approaches,” he writes, pointing to nutritional changes as a promising means of starving sugar-hungry cancer cells, and calling for randomized clinical trials to see if they work.

Mahabir notes that the study looked only at patients with stage III colorectal cancer, and that before making the leap to other forms or stages of cancer more research is necessary. But for now?

“The take-home message is this,” Mahabir says. “If you are a cancer patient, it would probably be a wise idea to include a dietary pattern that includes foods with a lower glycemic load.”